An exhaust gas recirculation (EGR) system in vehicle powertrain function to recirculate exhaust gases back into an intake system of an engine, with the intent to reduce NOx emissions. However, while reducing NOx, the exhaust gases inherently comprise a dirty environment including the by-products of combustion. Thus, over time soot and other carbon materials may build up in the EGR system. As one example, an EGR passage in the EGR system may become clogged due to carbon buildup. In another example, an EGR valve positioned in the EGR passage may become loaded with carbon buildup, which may in some examples cause the EGR valve to exhibit degradation (e.g. stuck in at least a partially open position, or stuck in a fully closed position). An EGR valve that is stuck closed, or a clogged EGR passage, may result in increased temperatures in the exhaust system of the vehicle, which may lead to exhaust system degradation in some cases. Furthermore, undesired emissions may be increased in a vehicle with a clogged EGR passage or stuck closed EGR valve. In some examples, special additives may be utilized to clean an EGR system, however such methods may be intrusive and/or may require the vehicle to be serviced by a technician.
The inventors have recognized these issues, and have herein developed systems and methods to at least partially address them. In one example, a method comprises reducing a carbon buildup in an exhaust gas recirculation system of an engine of a vehicle, the exhaust gas recirculation system configured to route at least a portion of exhaust gas in an exhaust passage of the engine to an intake manifold of the engine, by injecting a diesel exhaust fluid into the exhaust passage, and routing the diesel exhaust fluid into the exhaust gas recirculation system. In this way, carbon buildup may be reduced in an onboard and on-demand fashion.
In one example of the method, routing the diesel exhaust fluid into the exhaust gas recirculation system may include rotating the engine unfueled in a reverse direction while the diesel exhaust fluid is being injected into the exhaust passage, for a predetermined duration. In such an example, subsequent to routing the diesel exhaust fluid to the exhaust gas recirculation system, operating the engine to vaporize the diesel exhaust fluid routed to the exhaust gas recirculation system.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.